This invention relates to the improvement of a device which can display, through a window, part of an image screen onto a visual screen.
A document processing device currently exists, which is capable of executing the creation/editing of a document, while simultaneously displaying the contents of the document. One of the display functions possessed by such a document processing device is a multi-window display function, which simultaneously displays separate information on a single visual screen, through different windows. This multi-window display function is used as a means to improve a man-machine interface.
There is a document-processing device with a multi-window display function which displays a scale corresponding to the size of an image screen an marks the center or the start point of a window on the scale with a symbol. With this display function, however, an operator cannot easily ascertain the size of a window at a glance, in relation to the region within which the window can move, i.e., the region on the image screen in which the window can move and/or change its size.
This problem also occurs in a document-processing device which does not have a multi-window display function.
To set a plurality of windows on the image screen, it may be necessary to restrict the movable range of each window. However, the prior art does not offer a function for enabling the operator to properly ascertain the limit of the movable range.